Multiple-input multiple-output (MIMO) technology refer to a method of employing multiple transmit antennas and multiple receive antennas so as to improve transmission/reception data efficiency, unlike a conventional method using one transmit antenna and one receive antenna. That is, the MIMO technology refers to a technology of utilizing multiple antennas in a transmitting end and a receiving end so as to increase capacity and improve performance and may also be referred to as a multi-antenna technology. In order to accurately perform multi-antenna transmission, information about a channel needs to be fed back from a receiving end for receiving a multi-antenna channel.
Although one carrier is configured in uplink and downlink in a conventional wireless communication system, a carrier aggregation technology or a multi-carrier technology using a combination of a plurality of carriers has been introduced in order to support an extended bandwidth.